1. Field of Invention
This invention relates generally to communications systems, and more particularly to a battery saving system for a portable telephone system.
There are many applications wherein it is necessary to provide a battery saving system for a communications system. One such application for such a battery saving system is in a portable radio telephone system.
2. Prior Art
Several techniques for providing a battery saving system for communications system are known. Such systems generally employ a push to talk circuit wherein the transmitter of the portable unit is manually keyed by a push button or the like when it is desired to transmit a message, the transmitter normally being unkeyed when no message is being transmitted.
Whereas this system provides a way to reduce the power consumed by the portable unit, the system is impractical for portable telephone systems wherein automatic full duplex operation, such as is obtained with a normal telephone, is desired. Automatic full duplex operation has been provided in mobile telephone systems, which are mounted in vehicles, by rendering the mobile transmitter operative whenever the telephone hand set is removed from the cradle, however, the continuous operation of the mobile transmitter whenever the hand set is "off hook" requires more power than can be continuously provided by portable batteries, thereby making portable radio telephones impractical.